Electromagnet device



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"W995i M mi-mil J H MUTH ELECTROMAGNET DEVICE Flled Aug 27 1925 July 21, 1925.

Patented July 21, 1925.

UNITED STATES JOHN H. MUTH, OF EAST CLEVELAND, OHIO.

ELECTROMAGNET DEVICE.

Application filed August 27, 1923. Serial in. 659,489.

To all whom it may concern:

Be it known that'I, JOHN H. MUTE, a citizen of the United States, residing in East Cleveland, county of Cuyahoga and State of Ohio, have invented a new and useful Improvement in Electroinagnet Devices,

of which the following is a specification.

'My invention relates, generally, to devices having electro-magnets and an armature in operative association therewith and, particularly, to such devices'as are used in telephones and similar devices.

The main object of my invention is a simple and etficient electro-magnet device, in which the parts are convenient and economical of manufacture, in which the parts are easily assembled or dis-assembled, in which the parts are easily accessible for inspection and repair, in whlch the magnetic lines are directed and distributed for most effective and desirable action of the magnet poles on the armature, and in which the hysteresis losses are reduced to a minimum. Other objects will appear during the description of the devices shown in the accompanying drawing. I

By way of exemplification, I have shown my lnvent-ion, in the accompanying drawing, as embodied in a telephone receiver in different combinations and effects to illustrate my invention clearly. It is understood, however, that such embodiment can be extended to devices other than telephone receivers, as shown or otherwise, and that the specific construction and arrangement of elements shown is-susceptible to changes and modifications to meet varying conditions either of the application or the operation of my invention or of the application or the operation of the parts thereof.

In this accompanying drawing, Fig. 1 1s a plan view of a telephone receiver, without the cover, embodying the features of my invention; Fig. 2 is a section, taken on a vertical plane indicated by the line 22 in Fig 1, showing a certain arrangement of the electro-magnet and one style of angularly disposed legs for the electronagnet; Fig. 3 is a section, similar F g. 2, showing another style of legs; Fig. 4 is a section, similar to Fig. 2, showing another the aligned surfaces 18 and 19 termmatmg style of legs and heads on these legs; Fig. 5 is a plan view of Fig. 4, without the cover, showing one contour of the heads in relation to the diaphragm; Fig. 6 is a section, similar to Fig. 2, showing no heads on the legs but a head on the diaphragm; Fig. 7 is a plan view of Fi 6 showing a certain relation between the ead and the ends of the legs; Fig. 8 is a section, taken on a vertical plane indicated by the line 8 in Fig. 4, showing further relation between the heads and the legs and the diaphragm; and Fig. 9 is a section, taken on a vertical plane indicated by thevline 9 in Figs. 2, 3,

4, and 6, showing the relation between the cap and the legs and the permanent magnet. Similar reference characters refer to similar parts throughout the views.

The telephone receiver shown in the drawing consists, principally, of the case A, the cover B, the diaphragm O, the permanent magnet D, the magnet legs E, and the coils F.

The case A is here shown as one of the usual forms with the upper end threaded and the cover B screwed thereon. The diaphragm C is disposed between the end of the case A and the inside of the cover B and is thereby supported by the outer edge or perimeter thereof as usual.

The electro-magnet, however, is here provided with "features which form the basis a for the present invention.

The permanent magnet B, suitably magnetized and adapted to retain this magnetism, is here formed rectangular, rests on the inside of the bottom 10 of the case A, is not confined sidewise' but is confined lengthwise by the ends thereof abutting the inside of the wall 11 of the case A, and is held to this bottom by the two screws 12 as seen in Fig. 2.

The legs E are each composed of laminae placed side by side as is usual in laminae structures and each of these laminae is formed with the foot portion 13 and the body portion 14 disposed at an angle to this foot portion so that the upper end of the legs converge as seen in Figs. 2, 3, 4, and 6 when thefelectro-magnet is assembled.

The upper ends of the laminae may terminate into points 15 as seen in Figs. 2 and 6, or intoupwardly projecting ends 16 as seen in Fig. 3, or into the ends 17 seen in Fi 4.

The upper ends of all of the legs ave a suitable distance below the diaphragm.

In the arrangement of the legs shown in Figs. 2 and 6, the points 15 may be brought very close together since the angular disposition of the legs provides a downwardly increasing air gap between the legs which reduces magnetic leakage across the magnet oles. In this construction, the area of the aces 18 and 19 is larger than the cross-sectional area of the legs; therefore the density of the magnetic lines in .the air gap 20 is less than in the legs themselves, so that the heads, hereinafter described, may be dis pensed with.

In the arrangement of the legs shown in Fig. 3, there is greater magnetic leakage between the magnet poles unless the ends 16 are spaced further apart; the density of the magnetic lines in the faces 18 and 19 is equal to the density in the legs, but the magnetic lines are here directed straight to the diaphragm.

In the arrangement of the legs shown in Fig. 4, there is some magnetic leakage between the magneto poles if spaced too close together, but the heads on the ends of these legs have a tendency to confine the magnetic lines to the air-gap 20.

In either case it is preferred to introduce the electrically insulating sheet 21 and,,in addition thereto, magnetic insulation material, such as zinc, bismuth, etc., may be introduced between these magnetic poles.

When the upper ends of the legs have the rectan ular surfaces 18 and 19, so far describe and the diaphragm is round and supported around the outer edge as is usually the case, all of the magnetic lines from the electro-magnet do not affect the diaphragm symmetrically about the center or from the circumference thereof; thereby causing a sort of distortion in the diaphra m which creates foreign vibrations or soun s.

In order to eliminate, or at least mitigate, these undesirable results, it is necessary that this uneven pull or action on the diaphragm be equalized. This I accomplish in one instance by providing heads on the magnet poles as seen in Figs. 4, 5, and 8 and in another instance by providing a. head on the diaphragm as seen in Figs. 6 and 7. All

of these heads serve the purpose of either' reducing the density of the magnetic lines in the air-gap, or to localize these lines in relation to the diaphragm, or both; the heads on the legs serve the additional purpose of confining the upper ends of the laminae.

The heads 22 (Figs. 4, 5 and 8)-are secured to the upper ends of the legs by solderin or otherwise and, preferably, have the ange 23 for better contact with the legs for the purpose of facilitating the passage of the magnetic lines as well as securing the heads to the legs.

It is observed that t is upper faces 24 of these heads 22 are semi-circular incontour (Fig. 5)-and thatall points on this contour are spaced the same distance from the common center of these heads and of the diaphragm, thereby directing and localizing the magnetic lines to a portion of the diaphragm e ually distant from the support thereof an exerting a pull or action thereon which does not distort it outside of the un dulations required to accomplish its desired purpose. The heads 22 are, preferably, made of material which can be magnetized but which does not retain magnetism.

The head 25 (Figs. 6'and 7) is made of material which can be magnetized but which does not retain magnetism and is secured to the diaphragm by the rivet 26 in the center thereof. It is observed that the shoulder 27 is comparatively small in diameter for the purpose of leaving this diaphragm as free as possible from incumberance and, to further aid in this direction,

head is made as light in weight as poss1 e.

It is further observed that the lower end 28 of this head 25 is circular in contour and that the edges 29 of the upper ends of the legs extend outside of this circular contour. The object of this arrangement is to direct and localize the magnetic lines to the center of the diaphragm. The air-gap 20 is here located between the upper ends of the legs and the lower end of head 25 and the magnetic lines cross this air-gap. Those magnetic lines vrhich pass into or out of those portions of the faces 18 and 19 which are directly under the head 25 pass directly into or out of this head straight through the airgap, but those magnetic lines which pass into or out of those portions of the faces 18 and 19 which la outside of the contour of the head, pass oliliquely into or out of this head since the air-gap there is shorter than to the diaphragm; thereby directing and localizing the action of the magnet to the center of the diaphragm.

It may be noted here that the introduction of the head 25 permits the use of a diaphragm made of material other than iron or other magnetizalole material.

When the core of an electro-magnet is built up, particularly when a portion thereof is made up of laminae, it is necessary that the juncture of these parts is provided with sufficient contact area to 'ermit the magnetic lines to pass without an ue loss.

In all of the structures shown in the drawing, the foot of each leg is held firmly to the permanent magnet by the cap 30 which fits over the sides and over the top of the foot and extends some distance on each side of this foot at 31 as seen in Fig. 9. These portions 31 extend down to nearly the to 01 the permanent magnet, thereby provl mg additional surface for the passage of magnetic lines.

net.

These caps and the feet of the legs are held down on the permanent magnet by the screws 32 threaded 'intothe permanent mag- A suitable winding, comprising. the coils F, is placed over the body portion 14. or each of the legs; both ofthese'windings are electrically-connectedto .each other and tothe bindmg' posts 33' and 34 from which the leads'35 and 36 project outside of the casing through the opening 37 for outside.'connection. 5 3

In the leg structure shown in Figs.- 2 and 6, the heads may be omitted since thefaces 18 and 19 are larger injrea. than the cross section of the legs. These faces may be rounded as indicated b the dotted lines 38.

(Fig. --1) to'direct and ocalize the magnetic lines of the electro-magnet for concentric action on the diaphragm.

In the structure shown in Fi s. andti, the coils F can; be-wound individually and placed over the legs when, the device is assembled. In the structuresliown in Fig. 4, the coils F may be wound individually and placed over the legs when the device is assembled and the heads put on afterward. In

the structure shown in Fig. 3, the coils F should be wounddirectl "on the legs since they can not be slippe over the ends 16 unless the opening in the coils is suiiiciently largeto do so. r I

The angular disposition of the legs pro vides morewinding-space for the poles and permits of better direction and distribution of the'magnetic lines for action onthe dia-' phragm; the heads on the poles further ins crease such direction and distribution as well asto hold the laminae together. atthe poles, the laminae decrease hysteresis-the cap on the'teet of the legs promote the passage oi the magnetic lines, and the ma etic'. lines not onthe diaphragm concentrically. with the support'thereof.

It appears that the structure shown and"- described and ,pointed out are sufiicient to fully disclose my'invention; Modification may, however, be made as to arrangement of parts,'or construction thereof, or as to application of my invention to devices other.

than the telephone receiver shown and described. Therefore, without limiting myself to the precise application of my invention and details of construction thereof as shown and described,

I claim 1. An' apparatus of the character de scribed, including, an electro-magnet comprising a flat rectangular plate permanentl magnetized toform a magnetic pole at eac en thereof, a magnetizable leg rovided with a foot resting on each of sai ends, a

ca contacting the top and both sides of each 0 said feet and the corresponding of said ends of the plate to increase the contact area between said feet and said plate, and a coil over each of said legs.

2. An, apparatus of the character described, including, an electromagnetcomprising a flat rectangular plate permanently magnetized to form a magnetic pole at each end thereof, a magnetizable leg composed of scribed, including, an electro-magnet comprising a'flatrectangular plate permanently magnetized to form a magnetic pole at each. end thereof, a magnetizable leg extending upwardfrom each of said ends of the plate, each of said legs composed'of a body portion and a' foot'portion', saidbody portion of the legs convergent opposite said plate, means for clampingsaid foot portions to said ends of the plate,and a coil over each of said body portions of the legs.

4. An apparatus of the character described, including, a diaphragm supp rted by the perimeter thereof, an electro-magnet comprising a fiat rectangular plate perma nently magnetized to form a magnetic pole at each end thereof, a magnetizable leg-cormposed of laminae extending upward from each of said ends of the plate, a head on the upper end of each of said legs to hold said laminae together, the joint contour of both of saidheads concentric with the support for paid diaphragm and ajcoii for each of said An a paratus of the character describ'ed,'inc uding, a diaphragm supported .by the perimeter thereof, an electro-magnet and the two sides of each of said feet legs extending upward from this plate, a I

, head on the end of each of said legs adjacent said diaphragm, and the contour of both of said heads concentric withthe support for said diaphragm. u I

-'7. An apparatus of the character de ribed, including, a diaphragm supported by the perimeter thereof, an electro-magnet having a permanently magnetized plate and legs composed of laminm, each of said legscomposed of a body portion and a foot portion, a cap encompassing the top and the two sides of each of said foot portions to hold said laminae together and secured to said plate,'a head on the end of each of said body ortions to hold said lamina together, and t e joint contour of both of said heads concentric with the support for said diaphragm. I

8. An apparatus of the character described, including, a diaphragm supported by the perimeter thereof, an electro-magnet com rising a fiat rectangular plate permanent y ma netized to form a magnetic pole at each en thereof, a magnetizable leg com- .posed of laminae on each of said ends of the plate, each of said legs composed of a body portion and a foot portion, said body portions convergent opposite said plate, a cap encompassing the top and the two sides of each of said feet to hold said laminae together and to increase the contact area between said feet and said plate, means for clamping said caps to said plate, and a coil for each of said le s.

'9. As an article of manufacture, an electroneaaeoa magnet for an acoustical instrument, a plate and with a foot portion on one end thereof and resting on one of said ends of the plate, and individually wound coils adapted to he slipped over said body portions of the legs.

10.. As an article of manufacture, an electro-magnet for an acoustical instrument, a plate formed flat and rectangular and magnetized to form a magnetic pole at each end thereof, a pair of legs formed of laminae, each of said legs formed with a straight body portion and a foot portion on one end thereof and disposed at an obtuse angle to this body portion and resting on one of said-ends of the plate, individually Wound coils adapted to he slipped over said body portions of the legs, a cap encompassin the major portion of each of said feet an contacting said plate, andmeans for securing said caps to said plate.

JOHN H. MUTH. 

